Laser ultrasonics-based material analysis system and method utilizing lamb modes

Abstract

An interferometric system for measuring a property of interest of a target, such as temperature, by detecting the velocities of the symmetric S o ) lamb modes and anti-symmetric (A o ) lamb modes.

What is claimed is: 
     
       1. A system for determining a characteristic of a target having a thickness suitable for supporting Lamb modes, comprising: means for launching an elastic wave within the target;   an interferometer for detecting a displacement of a surface of the target in response to said launched elastic wave;   means, responsive to said detected displacement, for determining a velocity of an elastic wave corresponding to a symmetric (S o ) Lamb mode and a velocity of an elastic wave corresponding to an anti-symmetric (A o ) Lamb mode within the target; and   means for correlating said determined S o  Lamb mode and said A o  Lamb mode velocities with a property of interest of the target.   
     
     
       2. A system as set forth in claim 1 wherein a frequency of the elastic wave is made a function of the thickness of the target so as to substantially eliminate a dispersive characteristic of the elastic wave. 
     
     
       3. A system as set forth in claim 1 wherein said property of interest is temperature. 
     
     
       4. A system as set forth in claim 3 wherein the target is comprised of a silicon wafer.